Chapter 3: Idependent Assortment

Question 1

Dihybrid cross

Answer 1

An individual who is heterozygous for two genes.

Question 2

Summary of Mendel’s second law: Independent assortment (phase of meiosis+ what happens+the 2 results)

Answer 2

In metaphase I, homologous pairs line up at metaphase plate independently from others. Either recombinant form or parental.

Question 3

Idepenent assortment results in gametes which are 50% ____(diff from parental genotypes)

Answer 3

recombinant

Question 4

How is a dihybrid cross set up and what is produced and explain it?

Answer 4

two heterozygote crossed for 2 genes
- produces 9:3:3:1 ratio
- 9 is dominant of both trait
- 3 is dominant one trait not the other
- 3 is dominant second trait not the other
- 1 is all recessive

Question 5

what does this formula mean?
1-(15/16)^n=0.95

Answer 5

Solving this equation for n gives us the number of progeny required to give a 95% chance of success for obtaining required genotype

Question 6

when solving for n how do we manipulate the formula 1-(15/16)^n=0.95 to our own problem?

Answer 6

Find the probability of obtaining your desired genotype via the product rule (see pic below) and then do the minus with full from that number (ex: if prob= 1/4, then use 3/4) and use that number in place of (15/16).

Question 7

dihybrid cross DF=

Answer 7

3

Question 8

Dihybrid test cross always produce the phenotypic ratio of:

Answer 8

1:1:1:1

Question 9

Penetrance

Answer 9

The % of individuals with a mutation that show the phenotype

Question 10

Incomplete/variable penetrance

Answer 10

Some individuals with a mutant genotype will not show the phenotype
Ex: Osteogenesis: a fodminant disorder of bone formation but some never develop symptoms

Question 11

Expressivity

Answer 11

Differing levels that a phenotype is expressed

Question 12

Variable expressivity

Answer 12

Some individuals show differing degree of phenotype
Ex: Polydactylyl : some affected cats have differing # of toes

Question 13

Recessive Epistasis+ex+ratio

Answer 13

When the phenotype of a mutant allele masks the phenotype of the mutant allele of another gene
Ex: bald mutant mask curly hair genotype
9:3:4

Question 14

Dominant epistasis example+ratio:

Answer 14

Dominant armless mutation mask recessive long finger mutation

12:3:1

Question 15

Supressor Mutations+ratio

Answer 15

Reverse the effect of mutation in another gene, results in wild type

13:3

Question 16

Synthetic mutations+ratio

Answer 16

Mutation in 2 different genes individually do not cause a phenotype but together result in a mutant. Ex: both a/b work tut to turn on the expression of a target gene but the mutant allele when they are both not WT doesn’t produce the turn on effect.

Ratio: 15:1